1. Field of the Invention
The present invention relates to a medium recording a color transformation lookup table for color transformation on printing, a printing apparatus and a printing method both using the color transformation lookup table, a medium recording a printing program, a color transformation apparatus, and a medium recording a color transformation program.
2. Description of the Prior Art
Image processing devices such as displays, printers have the device-dependent color gamut, that is, the range of colors producible by the device. When two image processing devices are compared in the aspect of colors, generally, some colors are producible on both devices; other colors are producible only on either device. For some image processing devices, despite having the ability of fine color reproduction, it was conventionally practiced to limit their color gamut to a certain extent enough to make their output look in homogenous colors to the human eyes. For example, assume that an image on a display is printed by a printer. In a color region where the color gamut of the display is wider than that of the printer, the colors visible on the display are mapped to fall within the color gamut of the display and the color gamut of the printer. Colors in another color region where the color gamut of the printer is wider than that of the display are not used when images are printed.
For conventional color transformation programs based on the above-described color-mapping method, a problem was posed which will be described below.
If an image presented on the display is printed, using the colors in a region that fall within both color gamuts of the display and of the printer, the colors of the printed image well match the colors of the image on the display. However, because colors out of the color reproducible range of the display are not produced by printing, best-quality print results are not always produced. For example, when printing a photograph including colors in the range of the green hue to the blue hue wherein the color gamut of the printer is wider in the direction of chroma rise, the colors of its print result will be poorer in tones than the colors of the actual subject.
To solve the problem, an object of the present invention is to provide a medium recording a color transformation lookup table, printing apparatus, printing method, a medium recording a printing program, a color transformation apparatus, and a medium recording a color transformation program, in order to permit an image processing device to produce desirable color image outputs by making more effective use of its color gamut.
In accordance with one aspect of the present invention, a medium recording a color transformation lookup table is provided. The color transformation lookup table is referenced for transformation of first color image data used on a first image processing device into second color image data used on a second image processing device and has a first set of values and a second set of values which represent a relationship between color gamuts of the first image processing device and the second image processing device,
wherein if there exists the region that is out of the color gamut of the first image processing device but falls within the color gamut of the second image processing device in a certain hue of the device-independent color space, the relationship is equivalent to the relationship of color gamut determined, based on gamut mapping in a predefined device-independent color space, through a process comprising:
a color gamut shift step to obtain the mapping which expands the shape of the color gamut of the first image processing device so as to be close to the shape of the color gamut of the second image processing device in a homogeneous hue range; and
a color gamut expansion step to obtain the mapping which expands a certain region of the resulting gamut processed at the color gamut shift step into the inside of color gamut of the second image processing device.
In the present invention of this aspect, by using a color transformation program that comprises the steps of inputting the first color image data for use on the first image processing device and transforming the first color image data into the second color image data for use on the second image output program, the first color image data is transformed into the second color image data, based on the relationship between color gamuts of the first image processing device and the second image processing device, which has been defined by the color gamut shift step. The color gamut shift step performs gamut mapping in which the shape of the color gamut of the first image processing device expands so as to be close to the shape of the color gamut of the second image processing device. In the predefined device-independent color space, this step is carried out in a hue in which a color region exists that is out of the color gamut of the first image processing device, but falls within the color gamut of the second image processing device.
When shifting the color gamut of the first image processing device, expansion rather than compression takes place so that the shape of the color gamut will be made close to the shape of the color gamut of the second image processing device. Consequently, if the color gamut of the second image processing device is wider than that of the first image processing device, the resulting gamut by shift maintains the characteristics of the color gamut of the first image processing device, while it is close to the characteristics of the color gamut of the second image processing device. Color gamut shift can take place without unnatural color transformation. By making the color gamut of the first image processing device close to the color gamut of the second image processing device, the region expands where the color gamut of the first image processing device overlaps with the color gamut of the second image processing device. This makes it possible to decrease the number of colors that are out of the color gamut of the second image processing device and increase the number of colors available on the second image processing device.
In order to obtain images with finer tones in a hue in which a color region exists that is out of the color gamut of the first image processing device, but falls within the color gamut of the second image processing device, following the color gamut shift step, the color gamut expansion step is carried out for gamut mapping in which a certain region of the resulting gamut after the color gamut shift further expands into the color gamut of the second image processing device. Consequently, the gamut obtained by shifting the color gamut of the first image processing device through the color gamut shift step is further modified to include colors that are out of the color gamut of the first image processing device, but fall within the color gamut of the second image output.
Color transformation of the first color image data into the second color image data, based on the finally obtained gamut, enables effective use of colors that are out of the color gamut of the first image processing device, but fall within the color gamut of the second image output. By using the color gamut shift step in combination with the color gamut expansion step as required, both unnatural color transformation prevention and effective use of the color gamut of the second image processing device can be achieved at the same time. The above-described process can be augmented by adding another step. For a region that still falls out of the color gamut of the second image processing device after the execution of the color gamut shift and color gamut expansion steps, it is advisable to compress the region into the color gamut and define the gamut mapping relationship between the first and second image processing devices.
In this way, according to the present invention, unnatural color transformation can be prevented with effective use of the color gamut of the second image processing device. Because color transformation is executed by simply referencing the color transformation lookup table, it is not necessary to execute the color gamut shift and color gamut expansion steps whenever transforming the first color image data into the second color image data. Thus, the resources or the like for performing the color transformation function can be saved.
As the device-independent color space, any of diverse color space schemes such as Lab, XYZ can be adopted as color space. The first and second image processing devices are not limited to specific ones and may be any device that reproduces images, using color image data such as displays, printers, scanners, digital cameras. These devices are not always separate ones. For example, a fax machine has a scanner as the first image processing device and a printer as the second image processing device, which are integrated therein, and the present invention can be applied to the fax machine. The above-described process does not actively cause color variation when being carried out in a certain hue. However, some color variation is allowable as difference between the hue of the second color image data and the hue of the first color image data due to the property of the device-independent color space in which the process is carried out, the transformation between spaces, and the device-dependent error of an image processing device, etc. Even if the process does not actively cause hue variation, hue variation of xe2x80x9c0 to 10xe2x80x9d degrees may take place over the region for which color gamut shift is executed.
To reflect the foregoing relationship of color gamut in image output, transformation of the first color image data into the second color image data is executed by referencing the lookup table created in advance. Owing to the information obtained about the relationship between the color gamuts of the first image processing device and the second image processing device defined in the lookup table created in advance, it is not necessary to execute the color gamut shift and color gamut expansion steps whenever transforming the first color image data into the second color image data. Thus, the resources for performing the color transformation function can be saved.
Requirements for the lookup table are containing data that defines the relationship between color gamuts of the first image processing device and the second image processing device so as to enable transformation of the first color image data into the second image data. In building this table, any of diverse method can be adopted. For example, one method is such that the table is built by mapping typical color data as the first color image data to corresponding data as the second color image data and color data for any point is calculated by interpolation. Another method is such that the table is built by mapping typical color values by the coordinates of the color gamut of the first image processing device to corresponding color values by the coordinates of the color gamut of the second image processing device in the device-independent color space and color values at any coordinates are calculated by interpolation.
By way of illustration, as suitable devices to which the present invention is applicable, the first image processing device is a display and the second image processing device is a printer. In this embodiment, the color transformation function is performed to transform the first color image data expressed in an RGB color space into the second color image data expressed in a CMYK color space on the assumption of the following. The first color image data is expressed in the predefined device-independent color space, the color gamut shift step or/and the color gamut expansion step are executed, and then the second color image data is obtained, based on the finally obtained gamut data in the predefined device-independent color space.
To perform management of color compatibility between the display and printer, it is required that a specific device-independent color space intervenes therebetween in transforming the first color image data expressed in the display""s device-dependent or device-independent RGB color space into the second color image data expressed in the printer""s device-dependent CMYK color space. By thus performing the above-described process of the present invention in the device-independent color space, the management of color compatibility as well as the above-described unnatural color transformation prevention and effective use of the color gamut of the second image processing device can be accomplished.
By comparison of the display""s color gamut and the printer"" color gamut, around the green hue to the blue hue, such a tendency is found that the display""s color gamut is characterized by higher chroma in the high lightness range and the printer""s color gamut higher chroma in the medium and low lightness range. In other words, the display""s color gamut is greater in the high lightness range and the printer""s color gamut is greater in the medium and low lightness range. On the assumption that the present invention is applied to the display and printer, the invention enables effective use of the printer""s color gamut in the medium and low lightness range, so that print results featuring finer tones around the green hue to the blue hue can be produced.
Colors constituting the color gamut of an image processing device can be expressed by combinations of a plurality of color components. Color components used to express colors in a color space are usually three colors, but three colors are not always used for defining the relationship between color gamuts. Before or/and after the color gamut shift and color gamut expansion steps, the first set of values and second set of values of a color transformation lookup table are defined after increasing or decreasing the number of color components in a color space to which the color gamut belongs.
Specifically, by means of the color separation into color components, three color components in the device-independent color space can be changed to any number of color components. The relationship between the color gamuts of the first color data and the second color data can be defined to directly match the number of color components used by the image output device. For example, if the second image processing device is a printer, it is conceivable that color components such as four CMYK colors, six colors of CMYK plus lc (light cyan) and lm (light magenta), seven colors of CMYKlclm plus DY (dark yellow) are available on the printer. Once RGB color data from the display""s color gamut has been mapped to CMY color data, the CMY color data is transformed into CMYK color data or the like by color separation into color components, so that RGB color data can easily be mapped to CMYK color data or the like.
In this way, the relationship between the color gamuts of the first color data and the second color data directly matching the number of color components used by the image output device can be obtained.
Requirements for the color gamut shift step are that it is capable of gamut mapping in which the shape of the color gamut of the first image processing device expands so as to be close to the shape of the color gamut of the second image processing device in a homogenous hue range. Requirements for the color gamut expansion step are that it is capable of gamut mapping in which a certain region of the resulting gamut after the color gamut shift further expands into the color gamut of the second image processing device. In one embodiment, it is advisable to effect these steps as follows. The color gamut shift step causes lightness to decrease and chroma to increase based on the coordinates of the device-independent color space; meanwhile the color gamut expansion step causes chroma to increase while keeping lightness nearly constant, based on the coordinates of the gamut processed at the color gamut shift step in the device-independent color space.
Among three attributes colors, i.e., hue, lightness, and chroma, the human eyes are normally most sensitive to hue change. Accordingly, the above-described process of the present invention does not actively cause hue change, or hue variation. As the color gamut shift step causes lightness to decrease and chroma to increase, the present invention can function effectively in circumstances where the color gamut of the first image processing device is greater in the high lightness range and the gamut of the second image processing device is greater in the medium and low lightness range. By decreasing lightness while increasing chroma, gamut mapping that does not cause unnatural color appearance to the human eyes can be obtained. As the color gamut expansion step causes chroma to increase while keeping lightness constant, the present invention can function effectively in circumstances where the gamut of the second image processing device extends wider in the high chroma range. In consequence, the second image processing device outputs fine tone color images.
In view of the foregoing, it is advisable to effect the color gamut shift step as follows. The mapping in the color gamut shift step is obtained in such a manner that the higher the chroma point is in the color gamut of the first image processing device in a certain hue, the greater the displacement by shift is. That is because difference in gamut shape between the image input device and output device is significant in the high chroma range, when the color gamut is expressed in the color space based on the lightness, chroma, and hue coordinates. Thus, when shifting the color gamut of the image input device, shifting the contour of its protrusion toward rise in chroma is important. Significant shift in the low chroma range may cause inherently little colorful colors to become colorful. Thus, the displacements are set such that more shift will take place in the higher chroma range. In consequence, color gamut shift without causing unnatural color appearance can be accomplished while significantly shifting the color gamut of the first image processing device so that it will expand so as to be close to the color gamut of the second image processing device.
The above-described color gamut shift step is executed for each hue and the color gamut shift results for all hues must give color values without causing unnatural color appearance as a whole. In view hereof, in yet another embodiment, it is advisable to effect the color gamut shift step as follows. The color gamut shift step varies the displacement by shift according to any of or combination of hue, chroma, and lightness of the color image data which have not processed at the color gamut shift step. The region where the color gamut of the second image processing device is greater than the color gamut of the first image processing device changes, depending on the hue, lightness, and chroma values.
By changing the displacement by shift for each hue, shift can exactly follow the color gamut change in terms of hue. By changing the displacement by shift for each lightness value, shift can exactly follow the color gamut change in terms of lightness. By changing the displacement by shift for each chroma value, shift can exactly follow the color gamut change in terms of chroma. By gradually changing the displacement by shift, according to the change in hue, lightness, chroma, tone jumps by mapping can be prevented. The color gamut somewhat differs, depending on the image processing media, device type and used ink of the second image processing device, and the image display device. It is also possible to slightly change the displacement by shift for adjusting such difference.
In view of the foregoing, it is advisable to effect the color gamut expansion step as follows. In the color gamut expansion step, the displacement by expansion of the chroma is set up in such a manner that the higher the chroma is which has not processed at the color gamut expansion step, the greater the displacement is. To make tones of images finer for higher chroma available and generate gamut mapping for producing fine tone images, it is necessary to expand the gamut by rising chroma. Significant chroma rise in the low chroma range may cause inherently little colorful colors to become colorful. Thus, the displacements are set such that more expansion will take place in the higher chroma range. In consequence, the resulting gamut mapping enables effective use of the gamut of the second image processing device and production of fine tone images. In further embodiment, it is advisable to effect the color gamut expansion step as follows. In the color gamut expansion step, the chroma expansion is not performed on a certain region where the chroma of the color image data which have not processed at the color gamut expansion step is small. This can prevent gamut expansion from causing inherently little colorful colors to become colorful.
The above-described color expansion shift step is executed for each hue and the color gamut expansion results for all hues must give color values without causing unnatural color appearance as a whole. In view hereof, it is advisable to effect the color gamut expansion step as follows. The color gamut expansion step causes displacement by expansion to vary according to any of or combination of hue, chroma, and lightness of the color image data which have not processed at the color gamut expansion step. The region where the color gamut of the second image processing device is greater than the color gamut of the first image processing device changes, depending on the hue, lightness, and chroma values. By changing the displacement by expansion for the hue, lightness, and chroma values, expansion can exactly follow the color gamut change in terms of hue, lightness, and chroma.
By gradually changing the displacement by expansion, according to the change in hue, lightness, chroma, tone jumps by mapping can be prevented. The color gamut somewhat differs, depending on the image processing media, device type and used ink of the second image processing device, and the image display device. It is also possible to slightly change the displacement by expansion for adjusting such difference. Furthermore, gradually changing the displacement by expansion, according to the change in hue, lightness, chroma can prevent gamut expansion from generating a region out of the color gamut of the second image processing device.
To accommodate different forms of color gamut of an image processing device, it is advisable to perform color transformation as follows. A plurality of color gamuts with different shapes is available to any of or combination of the first image processing device and the second image processing device, and the sets of values represent each relationship of color gamuts. If a plurality of color gamuts of different shapes of an image processing device are available and the same displacements by color gamut shift and color gamut expansion are applied to all gamuts, colors with chroma being over-emphasized or under-emphasized may be produced. For color gamuts, from the viewpoint of color transformation precision as well, it is desirable to perform color transformation using the color data mapping relationships defined for each color gamut.
The color transformation performed based on the color data mapping relationships defined for each color gamut prevents unnatural color transformation for each gamut and enables effective use of each gamut. Diverse circumstances can be supposed where color gamuts of an image processing device are available. For example, it can be said that the color gamut differs, depending on the kind of consumables. For a printer, its color gamut somewhat changes by the replacement of image processing medium and ink set. For a scanner, its color gamut somewhat changes by the change to document type such as translucent one, reflecting one. Moreover, the color gamut somewhat changes when the type of the image processing device changes, and even for the same device type, difference in gamut may occur between individual devices. The foregoing manner can accommodate such difference in color gamut.
To define color data mapping relationships for each color gamut, it is advisable to define the relationship in the color transformation lookup table by individual displacement by shift or/and displacement by expansion to be performed for each of the color gamuts in the device-independent color space. In the present invention, because gamut mapping relationship between the first and second image processing devices is defined by performing the color gamut shift and color gamut expansion steps, by performing these steps for each color gamut, the mapping relationships can be defined for each gamut. For each color gamut, it is not required that completely different methods of gamut mapping be used. Based on the same gamut mapping method, by using different values of its related parameters, different gamut mapping can be produced. However, it is not necessary to assign different values to all parameters for each color gamut and common values of some parameters can be used.
In gamut mapping that varies for each color gamut, it is advisable to effect the color gamut shift step as follows. In the color gamut shift step, the displacement by shift is set up in such a manner that the larger the color gamut of the second image processing device is, the greater the displacement by shift is. A greater color gamut of the second image processing device has a greater region out of the color gamut of the first image processing device. Shifting the gamut of the first image processing device by greater displacement can surely make it close to the gamut of the second image processing device. In consequence, in separate gamut mapping for each color gamut, the region expands where the color gamut of the first image processing device overlaps with that of the second image processing device. This makes it possible to decrease the number of colors that are out of the color gamut of the second image processing device and increase the number of colors available on the second image processing device.
In gamut mapping that varies for each color gamut, it is advisable to effect the color gamut shift step as follows. The color gamut shift step causes displacement in such a manner that if the shapes of the gamuts of the second image processing device differs from each other, the displacement by shift of the highest chroma point in the gamut of the first image processing device is varied. In the mode in which the color gamut shift step modifies gamut mapping in such a manner that the highest chroma point in the color gamut of the first image processing device in a certain hue shifts by the greatest displacement and the displacement by shift of other points decreases in proportion as chroma decreases, change to the displacement by shift of the highest chroma point significantly influences the displacement by shift of the entire color gamut. It can be said that the displacement by shift of the entire color gamut is defined by the displacement by shift of the highest chroma point. In this mode, by changing the displacement by shift of the highest chroma point for each color gamut, different gamut mapping for different gamut shape can easily be obtained.
Not only in the color gamut shift step, gamut mapping that varies for each color gamut can be performed in the color gamut expansion step as well. In the constitution thereof, the displacement by expansion in the color gamut expansion step is set up in such a manner that the larger the color gamut of the second image processing device is, the greater the displacement by expansion is. This manner of expanding the gamut of the first image processing device by greater displacement to a greater color gamut of the second image processing device enables effective use of the color gamut. A greater color gamut of the second image processing device has the wider region where chroma is relatively high. For the greater color gamut, by expanding the gamut of the first image processing device by greater displacement than expanding it to a smaller gamut of the second image processing device, thereby more vivid colors can be produced.
To obtain different gamut mapping for different color gamut shape, a mode is applied in which gamut mapping is adjusted for each color gamut by following the tendency that displacements increase in proportional to the increase in gamut size and this mode is important for an image processing device on which a plurality of color gamuts are available. However, the mode in which the displacements by color gamut shift and color gamut expansion are always set greater for greater gamuts doe not apply to all cases. The following is also possible. For a particular color gamut that belongs to the second image processing device and is smaller than another one of the device, the displacement by shift or/and expansion is set greater than for another one. In other words, when performing color gamut shift or/and expansion, it is possible to set displacements conflicting with the tendency that displacements increase in proportional to increase in gamut size.
In this way, it is possible to make color images uniform in impression when produced after color transformation.
As the result of color transformation of the present invention, color appearance of images output by the second image processing device is important. After color transformation is executed, the color appearance of images output by the second image processing device is visually checked and then final tuning may be required. Tuning in conflict with the tendency that displacements increase in proportional to the increase in gamut size is allowable. For example, if kinds of image processing media and ink sets can be used on a printer, the printer has color gamuts for each combination of image processing medium and ink set. Even if unnatural color transformation prevention and effective use of color gamut are achieved separately for each color gamut, change of image processing media and/or ink set may cause the printer to output color images that are different in color impression as compared with those produced before the change and the user may want to prevent such difference.
In such cases, the color appearance of an image produced with each combination of image processing medium and ink set may differ, depending on the relativity of one color to its surrounding color. If color gamut shift and expansion are executed straightforwardly with the displacements set in accordance with the tendency that displacements increase in proportional to the increase in gamut size, print results of the same image may look different in color impression. When uniform color impression even with color gamuts is reckoned important, tuning is performed, and the set displacements by color gamut shift and expansion may be in conflict with the above tendency for some color gamuts. Such tuning is preferable if uniform print results even with color gamuts are reckoned important and allowable in the present invention.
For color transformation purposes, not only the color gamut shift step and color gamut expansion step of the present invention, but also other steps may be taken from different viewpoints. Often, as the result of execution of the combination of the steps, the relationship between the color gamuts of the first image processing device and the second image processing device is defined. When the above relationship is defined as the result of processing including other steps, it may be preferable to set the displacements by color gamut shift and expansion in conflict with the tendency that displacements increase in proportional to the increase in gamut size to eventually obtain fine color appearance. Accordingly, such tuning is allowable.
In color transformation that is executed, based on color data mapping relationships defined for a plurality of color gamuts, it is advisable to obtain another lookup table as follows. The relationship of gamuts is obtained by correcting the sets of values which are stored in a certain storage area and represent a relationship of the gamut. This renders it unnecessary to store the respective lookup tables which represent the predefined relationships of all pairs of gamuts. Thus only a minimum number of lookup tables are required for storing such relationship with regard to a particular color gamut of the second image processing device, saving storage area. For the correction method, any of diverse methods can be adopted. For example, one method is as follows. The shape of a particular color gamut of the second image processing device and the tendency of change of mapping relationship relative to that shape, estimated in advance, are maintained. By comparison between the shape of any color gamut of the second image processing device and the above color gamut shape, how the color gamut has changed is determined, based on which the mapping relationship is corrected. Another method is as follows. By comparing the reference mapping relationship with regard to a particular color gamut of the second image processing device and that for another gamut thereof, only color data of difference is maintained. During the processing for color transformation, color data of difference from the reference mapping relationship about the particular color gamut is replaced.
To practice color transformation of the present invention, it is preferable that the user can choose whether to execute the color transformation. It is also advisable to take the following manner. The sets of values which represent the relationship with the application of color gamut shift or/and color gamut expansion and the relationship without the application of color gamut shift or/and color gamut expansion, are made and stored in a certain storage area; and the relationship is decided based on the mode which is selected in advance by a user.
In this manner, the user can choose whether to execute color transformation based on the mapping relationship defined by the execution of color gamut shift or/and color gamut expansion in accordance with the present invention or execute color transformation based on the mapping relationship in other way. Color transformation execution according to the mapping relationship defined by the execution of color gamut shift or/and color gamut expansion of the present invention is advantageous in that vivid color appearance is obtained and unnatural color transformation can be prevented. However, to meet the user""s need that may differ, according to circumstances, it is preferable to provide options including the color transformation in accordance with the present invention. For example, some users may make a fine adjustment of colors on the first image processing device and want exactly the same colors output from the second image processing device. For such users, it is difficult to output a color image to the user""s intention if the color transformation in accordance with the present invention is performed. Thus, it is convenient for such users that color transformation can be performed, based on the mapping relationship defined without the execution of color gamut shift and color gamut expansion of the present invention. This serves the user""s need that may differ.
Herein, color transformation lookup tables are prepared to maintain any or combination of the mapping relationship defined by executing the color gamut shift step, the mapping relationship defined by executing the color gamut expansion step, the mapping relationship defined by executing the color gamut shift step, and the color gamut expansion step; and to maintain the mapping relationship defined by without executing these steps. The mapping relationship defined by without executing these steps includes all mapping relationships not modified by color gamut shift and color gamut expansion. When executing color transformation, it is advisable that the mapping relationship to be selected can be specified by mode selected by the user beforehand.
For example, explicit modes such as color gamut shift mode, color gamut expansion mode, color gamut shift and expansion mode, and other mode may be applied. Alternatively, non-explicit modes such as vivid mode, moderate mode may be applied. Selecting a mode beforehand may be done at least before color transformation. As means for facilitating mode selection, any of diverse means may be taken; for example, default selection that may be set and reset at any time, a mode selection dialog box presented before color transformation.
Even if the above-described color gamut shift step and said color gamut expansion step are executed, hue variation can be limited to a small degree; for example, it can be restricted to 15 degrees or less in Lab space.
The above-described color transformation lookup table is used for printing after color transformation and the same color gamut shift step and color gamut expansion step can be employed in a printing apparatus. Conceivably, such apparatus may be put into operation in a stand-alone mode or integrated into some equipment or system and put into operation with another methodology. Not limited to a certain mode of operation, the concept of the invention comprehends a variety of modes in which the invention is embodied and appropriate modifications are permissible within the range of the invention.
The above-described color gamut shift step and color gamut expansion step can be implemented as part of a printing method.
These steps can be executed by a computer. In such cases, the color gamut shift and color gamut expansion steps are embodied in program code of a printing program that is stored on a medium. The medium may be a magnetic recording medium, a magneto-optic recording medium, or any other recording medium which will be developed in future, all of which can be considered applicable to the present invention in all the same way. Embodiment of the present invention as software and hardware combination makes no difference in the concept of the invention. Embodiment of the present invention includes such a manner that part thereof is recorded on a medium in advance and will be read appropriately as required. Furthermore, duplicates of the above medium as primary and secondary duplicate products and the like are considered equivalent to the medium without doubt.
According to the above-described steps in accordance with the present invention, color transformation lookup tables can be created before or when color transformation is executed. In view hereof, the present invention can be interpreted as a method of creating color transformation lookup tables.